reply to wmcbrine
Re: So why is this better for battery life? Good question! It uses the existing circuit-switched UMTS radio interface to deliver the voice call, rather than IP-based transport.
In a typical UMTS network, the voice codec in use is based on the Adaptive Multirate (AMR) framework, which allows the base station and handset to negotiate a bitrate based on cell congestion, and encodes your voice digitally. However, the widely used AMR codec, while having a full bitrate of 12.2 kbps, only encodes sounds within the 300-3400Hz range. This new codec has a typical bitrate of 12.65kbps and encodes 50-7000Hz, so it much more closely approximates the human voice.
AMR-WB is the codec that operators are using in VoLTE deployments as well, but that transport method is much more expensive from a battery life standpoint due to increased network overhead and signalling when compared with the highly power-efficient circuit-switched UMTS air interface. (see »en.wikipedia.org/wiki/Adaptive_M···Wideband for more)